What Are Our UAS Maintenance Responsibilities as a COA Agency? – Ask Steve

Another excellent question I’ve been asked is: “What Are Our UAS Responsibilities as a COA Agency?”

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As fast-paced and modern as the public safety drone world is, the current FAA guidance and rules departments should follow have not moved at the same pace. Yet, these are the regulations and directives we have to operate under.

A UAS flown by a public safety department is stated to fly as a Pubic Aircraft. The definition of what a Public Aircraft is can be found in “Title 49 of the United States Code (49 U.S.C.) §§ 40102(a)(41) and 40125.”

A common conundrum I run into is public safety pilots and departments that have yet to embrace the reality they have now stepped into a regulation and bureaucracy sandpit when operating a drone.

Having been a pilot since 1988 I have learned this fundamental FAA truth, none of the rules matter till something unforeseen happens, and then all of the rules matter.

My answer here contains authoritative information from FAA guidance I reference specifically about COA aircraft operations. Your drone is an aircraft and your flights under a COA are public aircraft operations.

My role as a public safety drone pro is the help educate pilots and departments on what the facts are. You might find them ridiculous or silly but this is the world you step into when you operate an aircraft in the National Airspace System.

In general, “Title 49 of the United States Code (49 U.S.C.) § 40102(a)(41) states that a public aircraft is (1) an aircraft used only by the United States (U.S.) government, or (2) an aircraft owned or operated by the government of a state, the District of Columbia, or a territory or possession of the United States, or a political subdivision of one of these governments.”

If you want to take a deeper dive into Public Aircraft Operations – Manned and Unmanned you should read this and this.

The most important fact to remember is that if you are flying for a pilot under a COA and not as a Part 107 pilot, not every flight you make is covered as a Public Aircraft Operation (PAO). As the FAA says, “A government entity may unintentionally conduct civil operations that would be subject to the regulations in 14 CFR. All government entities are advised to become acquainted with the basics of the statutory requirements.” But that topic is best tackled in another post or a specific question by a reader.

One misperception I hear is that as a COA agency, we can operate the UAS as we see fit, and that is somewhat true; we can’t forget the following statement, “Simply stated, the FAA has statutory authority to regulate the operation and maintenance of civil aircraft used in air commerce. However, we have no statutory authority to regulate public aircraft, except for operations in the national airspace system. Oversight of the regulatory compliance of “public aircraft” is assumed by the government entity while they have operational and maintenance control the aircraft.” If you are in the air you are in the FAA regulatory system.

The FAA also says, “If not excluded by regulation all operational maintenance requirements that are required to operate in the NAS must be complied with.”

While COA UAS on an actual PAO flight would not be a civil aircraft, AC 91-91 provides this advice, “The 14 CFR regulations specified in this AC are used to illustrate how the operator of a civil aircraft must comply with certain rules. Governmental agencies and private entities conducting operations with public aircraft are encouraged to comply, when practical with the regulations for the type of aircraft operated.”

Today I want to focus on the maintenance question.

Maintaining Public Aircraft Including UAS

Responsibility for Airworthiness

The current FAA guidance on maintaining public aircraft is from 2016. It is AC 91-91. Everything I will quote below is from AC 91-91 and the guidance “applies to any person/owner/operator-known here as “operator”-who engages in the operation and maintenance of public aircraft as part of a governmental function.”

When it comes to the requirement that the drone has an airworthiness certificate for operation, the following section applies, “The FAA enhances safety through certification of aircraft per Title 14 of the Code of Federal Regulations (14 CFR) part 21, and we encourage public aircraft operators to obtain an appropriate airworthiness certification. An operator makes an airworthiness certificate effective when the operator complies with all terms and conditions of the certificate.”

A COA agency can certify their drone as airworthy by obtaining a recognized airworthiness certificate through a recognized process. You can’t just buy a piece of paper that says your drone is airworthy. The FAA definition of airworthy in AC 91-91 is “Airworthy. An aircraft, aircraft engine, or component that conforms to its type design and is safe to operate.”

Section 2.1 states, “Responsibility for Airworthiness. Title 14 CFR part 91 states that the owner/operator of a civil aircraft is primarily responsible for maintaining that aircraft in an airworthy condition, including compliance with FAA Airworthiness Directives (AD). We recommend that public aircraft operators use one of the inspection or maintenance programs specified in part 91, § 91.409, as described in chapter 2 and subsequent paragraphs. The safety benefits gained from following the regulations are derived from structured procedures for performing maintenance that will ensure the continued airworthiness of an aircraft. The economic benefit comes from the structured program itself, where expenditures can be planned in the most cost-effective manner. This includes maintenance planning, obtaining replacement parts, and scheduling the aircraft for maintenance at repair facilities. Regardless of regulatory requirements, safety is paramount and you will enhance the safety of your operations by following the regulations.”

The fact a UAS manufacturer elects to stop the development and support of a UAS operated by a COA agency appears to create a problem for agencies when it comes to “Instructions for Continued Airworthiness (ICAs). ICAs are information developed per applicable airworthiness requirements, including applicable inspection tasks, intervals, methods, processes, and airworthiness limitations (AL), to maintain airworthiness throughout the aircraft’s operational life. Some aircraft are TC’d with ICAs, and these consist of airplane manufacturers’ manuals including an Aircraft Maintenance Manual (AMM), standard wiring practice manual (SWPM), the Manufacturer’s Maintenance Planning document (MPD), and Maintenance Review Board Reports (MRBR). These manuals contain information necessary for the continued airworthiness of an airplane. Operators will find this information provided by the aircraft manufacturer is the most concise maintenance information for a particular make and model aircraft. Most civil aircraft manufactured prior to January 28, 1981, were not required to have ICAs for the airplane. Instead, the requirement was for an AMM. For those ex-military aircraft that are used in public operations, operators may use military technical orders (TOs) as a source of maintenance information.”

The fact that a manufacturer AMM does not specify the time limit on parts, like motors, does not mean the UAS does not have a time life limit or life-limited parts. The UAS operator needs to determine it in the absence of manufacturer guidance.


The requirements for recordkeeping by a COA agency are extensive and should be expected to be produced in a random inspection or complaint investigation.

Here is what is required under Aircraft Records:

2.9.1 Recordkeeping.

Title 14 CFR part 91 provides record keeping requirements for civil aircraft operators. Public aircraft owner/operators, while not required, are also encouraged to keep aircraft records. The information in this AC can be used as a guide to establishing a recordkeeping system. Aircraft records provide continuity of maintenance on an aircraft. The records can be used to plan future maintenance as well as show completion of past maintenance and to what criteria that maintenance was performed. Records allow the owner/operator to ensure that proper data and procedures are used in maintaining the aircraft and to identify the person performing the maintenance. In addition, records allow owner/operators to track and identify components that are repaired or replaced and if an AD is issued, to determine applicability of that AD to their aircraft. For public aircraft, a recordkeeping system similar to that of a civil aircraft will facilitate transfer from public to civil operations and back. It should also provide for a seamless transfer of ownership from public to civil operators if the aircraft records are kept in a format similar to a civil aircraft operation. Maintenance records may be kept in any format that provides record continuity, includes required content, lends itself to addition of new entries, and provides for signature entry. Aircraft records should contain at least the following:

  1. Record of maintenance for each aircraft, engine, propeller, rotor, and appliance of an aircraft. As a practical matter, many owner/operators find it advantageous to keep separate or individual records since it facilitates transfer of the record with the item when ownership changes.
  2. The maintenance record entry should include a description of the work performed. The description should be in sufficient detail to permit a person unfamiliar with the work to understand what was done, and the methods and procedures used in doing it. A reference to the technical data used such as manufacturer’s manuals, service letters, service bulletins, work orders, FAA ACs and other data, which accurately describe what was done, or how it was done, should be referenced.
  3. The maintenance record entry should contain the date the work was completed. This is normally the date upon which the work is approved for return to service.
  4. The maintenance record entry should include the signature and certificate number of the person approving the work for return to service.

Note: Prior to a PAO aircraft being returned to civil operations a maintenance record entry is required for the completion of a conformity inspection, stating that all maintenance performed while under government contract meets all civil regulations. This record provides for a seamless transfer of ownership from public use to civil operation; a conformity inspection is required to ensure the aircraft meets all civil regulations.

2.9.2 Total Time In Service.

The maintenance record entry should contain the total time in service for each airframe, engine, propeller, and appliance (as applicable). Time in service, with respect to maintenance records is that time from the moment an aircraft leaves the surface of the earth until it touches down at the next point of landing and is expressed in hours, cycles, or both.

2.9.3 Current Status of Life-Limited Parts.

A current status of each life-limited part of each airframe, engine, propeller, and appliance that contain at least the following:

  1. Time in service since new, expressed in the appropriate parameter (hours, cycles, and/or calendar time);
  2. Time in service remaining to the specified life limit expressed in the appropriate parameter (hours, cycles, and/or calendar time);
  3. The specified life limit expressed in the appropriate parameter (hours, cycles, and/or calendar time); and
  4. A record of any action that alters the part’s life limit or changes the parameter of the life limit.

2.9.4 Time Since Last Overhaul.

The time since last overhaul of all items installed on the aircraft that are required to be overhauled on a specified time basis include at least the following information:

  1. An identification of the item that requires overhaul and its associated scheduled overhaul interval;
  2. The time in service since the last overhaul was accomplished;
  3. The time in service remaining until the next scheduled overhaul; and
  4. The time in service when the next scheduled overhaul is due.

2.9.5 Current Inspection Status of the Aircraft.

The current inspection status of the aircraft means a record that contains at least the following information:

  1. The time in service since the last inspection required by the inspection program under which the aircraft is maintained.
  2. The time in service remaining until the next required inspection under which the aircraft is maintained.”

Much more information on maintenance records can be found in AC 43-9C Maintenance Records.

Additionally, AC 43.13-1B appears to apply to UAS operations since a manufacturer may not provide sufficient documentation to comply with this AC that covers, “methods, techniques, and practices acceptable to the Administrator for the inspection and repair of nonpressurized areas of civil aircraft, only when there are no manufacturer repair or maintenance instructions. This data generally pertains to minor repairs.”

A PAO aircraft is not a civil aircraft but the AC contains an expectation of what the FAA is looking for when it comes to minor maintenance. Of particular interest is Chapter 3 regarding fiberglass and plastics.

Inspection Program Recomendations

When it comes to inspecting your UAS for continued safe operation AC 91-91 gives the following guidance of what you should be doing, “The aircraft inspection program should contain at least the following:

  1. The instructions and procedures to conduct the inspection.
  2. Necessary tests and checks.
  3. Inspection items and areas of the airframe, engines, propellers, appliances, and emergency equipment.
  4. A schedule for the inspections in terms of time in service of aircraft, engines, parts (life-limited parts), calendar time, number of airplane and engine cycles, or any combination of these.
  5. Additional program content, such as:
  • Special inspections for hard or overweight landings, turbulent air, extended out of service inspection, etc.;
  • System for controlling life-limited parts;
  • AD compliance control;
  • System for recordkeeping, and
  • Creation, approval, and recording of program revisions.”

Spare Parts or Replacement Parts

UAS used in COA operations as a Public Aircraft can’t just put any part on the UAS. AC 91-91 states, “Components to be installed on a public aircraft that are maintained using the guidance in this AC should follow the requirements noted in the CFRs. Spare components should be repaired or overhauled at a facility such as a CRS or certificated air carrier. Owners/operators should use the component manufacturer’s recommended CMM when repairing or overhauling a component. In addition, eligibility for installation should be determined if the component is being installed on a TC’d airplane. The times and cycles on a particular component should be tracked in case the component is subject to a life limit or an AD.”

A cardinal rule you should embrace as a pilot is it does not matter what a salesperson or retailer says about if you can add an aftermarket part to your UAS. Everything they have to say is irrelevant. Your prevailing guide is what FAA opinion and documentation state.

COA operations, including the pilot and named responsible person, have the full and joint liability to make certain any added or replaced part meets the guidance found in AC 91-91.

If there is any doubt on how to treat replacement parts or add-, read AC 91-91, and if you disagree with what the official guidance says, make sure you get a written letter of opinion from your regional FAA FSDO to protect you and your department.

Who Can Perform Maintenance

You will need to make sure any internal or external people maintaining your UAS meet industry-standard or certified training programs through the UAS manufacturer. Outside entities may also provide training that meets the manufacturer’s maintenance and training standards.

“Under most circumstances, training programs for maintenance personnel are not required in part 91. Owner/operators of public aircraft can usually find training programs for their specific aircraft through the aircraft, engine or propeller manufacturer. They may also be able to contract with another operator or air carrier to provide training. Determining the training level of persons performing maintenance for an owner/operator of public use aircraft is essential in assuring safety and the airworthiness of the aircraft.

When Your UAS is Returned to Service

“This is a term that is used in civil aircraft operations when an aircraft is put back into service after maintenance, preventive maintenance or alterations are performed. Prior to aircraft return to service the owner/operator should prepare an appropriate entry in the aircraft log. Part 43 prescribes the rules governing the maintenance of aircraft having a U.S. Airworthiness Certificate and must be followed if the aircraft has a U.S. Airworthiness Certificate. The FAA recommends that public use owner/operators utilize those persons for return to service of their aircraft.”


The advice and regulations for maintaining a UAS as a COA aircraft do still far under older guidance for Public Aircraft. I have confirmed with the FAA that as of the publication of this post, those Advisory Circulars are still in force and apply to COA UAS operations.

What Are Our Uas Maintenance Responsibilities As A Coa Agency? – Ask Steve

My recommendation is to develop a comprehensive record-keeping solution for each aircraft. I have always found that a written logbook for the aircraft like one of these is easier to use. This is the one I personally use. You should have a specific logbook that goes with the aircraft. Buyers purchasing a used PAO drone should demand to see the logbook for that specific aircraft prior to purchasing.